Railway signal control system



March 27, 1951 J. H. BUTRIDGE ErAL RAILWAY SIGNAL CONTROL SYSTEM 2 sheets-sham 1 Filed OCT.. 6, 1948 dye and March 27, 1951 J. H. BUTRIDGE ErAL l y2,545,331

RAILWAY SIGNAL' CONTROL SYSTEM Filed Oct. 6, 1948 2 Sheets-Sheet 2 JNVENTORS Jamesflapidge and N Ilia l Claas 'la Y M@ THEIR ATIwz/VEY Patented Mar. 27, 1951 James H. Butridge, Kankakee, and William H. Claus, Downers Grove, Ill., assignors to The Union Switch and Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application October 6, 1948, Serial No. 53,112

` (c1. fammes) 7 Claims.

' Our invention relates to a railway signal control system, and particularly to a control system for signals for governing trafc movements in opposite directions over a stretch of single track railway.

In a railway signaling system of the wellknown absolute permissive block type for a stretch of single track railway which is provided with passing sidings spaced along the single track, two pairs of head block signals each comprising an entering and a leaving signal are commonly employed for each passing siding for governing traic movements in opposite directions, and are placed one pair adjacent each end of each passing siding. One or more pairs of intermediate signals for governing trac movements in opposite directions are also commonly employed between consecutive passing sidings. Protection for opposing traffic movements between passing sidings is obtained by suitable arrangement of the intermediate signals or by overlapping controls for the opposing leaving head block signals.

One feature of our invention is the provision ofan overlapping control arrangement vfor opposing head block signals, in which coded track circuits are employed for the stretch of single track between each two consecutive passing sidings, and non-coded track circuits are employed between the pairs of head block signals at the two ends of each passing siding.

Y Another feature of our invention, in an overlapping control arrangement for opposing head block signals in which coded track circuits are employed between passing sidings, is the requirement of only two line control conductors between each two consecutive passing sidings, and four line control conductors between the pairs of head block signals at the two ends of each passing siding.

An advantage of controlling the signals bef tween passing sidings of a singletrack stretch partially by coded track circuits andpartially by direct current line circuits, in our invention, isuthat, because of using coded track circuits foronly one direction of tranic movements, it has been possible to keep the track circuits uncomplicated,` although three diiferent code frequencies are employed, andat the same time, because of using the coded track circuits, only two line control conductors are necessary.

l'We shall describe one form of apparatus embodying our invention, and shall then point out the,` novel features thereof in claims. 1 e-#The accompanying drawings, Figs. 1a and 1b,

when placed end to end with Fig. la on the left, constitute a diagrammatic view showing one form of apparatus embodying our invention, in which a stretch of single track railway is provided with passing sidings spaced along the single track railway, and in which two pairs of head block signals are employed for each passing siding andv are placed one pair adjacent each end of each passing siding, and one pair of intermediate signais is employed between consecutive passing sidings for governing trafiic movements in opposite directions; and in which coded track circuits are employed for the stretch of single track between each two consecutive passing sidings, and non-coded track circuits are employed between the pairs of head block signals at the two ends of each passing siding, for providing an overlapping control arrangement for opposing entering head block signals and for opposing leaving head block signals. E Y Similar reference characters refer to similar parts in each of the drawings.

In each of the drawings, the contacts operatedv by the various relays or other devices are identied by numbers, each such number having a distinguishing prex, from which it is separated by a dash, when' the associated contact is shown apart from the relay by which it is operated. The prefix for each of these contact numbers comprises the reference character for the respective relay by which the associated contact is operated. For example, contact 6HDP-49, shown in the lower right-hand portion of Fig. la, in a pickup circuit for relay 5SR, is identified by the number 49 separated by a dash from the prefix (5I-IDP which is the reference character for relay tHDP by which this contact is operated. Referring further to the drawings, a portion of a single track railway is shownprovided with passing sidings X and W. In order to simplify the drawings, each track, comprising two paralleli seriesY of track rails, is represented by a single line. l The portion of the single track railway shown in the drawings is divided by insulated joints l2 to form sections, each of which is designated by the reference character T preceded by a distinguishing numerical prefix.

Each of the track sections 2T and 3T between the two pairs of head block signals at siding X, and each of the track sections 8T and 9T between the two pairs of head block signals at siding W is provided with a non-coded track circuit including a suitable source of current, such as a battery I 3, connected across the rails adjacent 3 ne end of the section, and a track relay, designated by the reference character TR with a distinguishing prex corresponding to that in the reference character for its section, connected across the rails adjacent the opposite end of the section.

Each of the sections 5T and 6T between the two consecutive passing sidings X and W is pro-v vided with a coded track circuit including a suitable source of current, such as a battery I4, connected across the rails adjacent one end of the section through a contact of a polar biased code repeating relay, and a track relay of the polar biased code following type, designated by the reference character TR with a distinguishing prefix corresponding to that in the reference character for its section, connected across the rails adjacent the opposite end of the section. A floating track relay of the polar biased code following type is also connected across the rails of' each of the sections 5T and 6T adjacent its battery I4. lThe floating relays are designated by the reference characters BATR and BATR, re spectively.

Each of the sections T and IIT, shown at the left-hand end of Fig. la, and at the righthandl end of Fig. lb, respectively, is also provided with a coded track circuit including a suitable source of current, such as a battery I4, connected across the rails adjacent one end of the section through a coding contact. Floating track relays IIATR and IIATR of the polar biased codefollowing type are also connected across the rails of sections GT- and I IT, respectively, adjacent the corresponding batteries I 4. It is to be understood that in an actual installation of a railway signal control system embodying applicantsY invention, a track relay of the polar biased code following type would also be connected. across the rails adjacent the opposite end of each of the sections 0T and IIT, similarly to relays GTR and STR of sections 6T and 5T, respectively. It is also to be understood that, in an actual installation embodying applicants invention, the coding contacts through which batteries I 4 are connected across the rails of sections 0T and IIT, would beoperated by polar biased code repeating relayscontrolled similarly to relays SCTP and SCTP, instead of being operated directly by a code' transmitter I80CT.

Decoding relays AFP and BABP are controlled by relay SATR. Each of these relays is made slow releasing, by a resistor r connected in multiple with its winding, so that each of these relaysl maintains its front contact closed during the open periods of contact 31 of relayv SATR, at its front and back points through which these relays are controlled. Relays BAFP and BABP are controlled by relay BATR similarly to the manner in which relays SABP and EAFP are controlled by relay BA'IR. Relays UAFP and llABP are controlled by relay BATR, and relays IIAFP and I IABP are controlled by relay I IATR similarly to the manner in which relays EABP and 5AFP are controlled by relay EATR.

Adjacent each end of each of the passing sidings is a pair of head block signals for governing traffic movements in opposite directions. Signals IS, 4S, 1S, and IGS which govern traic movements away from the passing sidings are known as leaving signals, whereas signals 2S, 3S, 8S, and 9S which govern traflic movements toward the passing sidings are known as entering signals. One pair of intermediate signals, designated b-y the reference characters 5S- and BS, governs trailic movements in opposite directions between the two consecutive passing sidings. Signals 2S, 4S, GS, 8S, and IUS govern trafc movements toward the right, as shown in the drawings, which we shall assume is the eastbound direction, whereas signals IS, 3S, 5S, 1S, and 9S govern traffic movements in the. opposite or westbound direction. The signals may be of any suitable design such, for example, as the searchlight type shown in the drawings, each of which comprises a lamp, not shown, and a mechanism designated by the reference character m with a pre1-lx corresponding to the prex in the reference character for its signal.

' rIwo circuit controller contacts designated by the reference characters I5 and I6, are operated in conjunction with each signal mechanism m. Each of the contacs I5 is closed at its front point. designated by the reference character G, when its signal mechanism is in .the clear position, and becomes closed at its back point, designated by the reference character R-Y, when its signal mechanism is operated to the caution or the. stop position. Each of the contacts I6 is normally closed at its back point, designated by the reference character R-G, while its signal mechanisrn is i-n the clear or the stop. position,l and becomes closed at a front point, designated by the reference character Y, when its signal mech-- anism is operated to the caution position.

As shown ior signals 3S and 8S, contact I5 or each entering signal, in the clear position, controls a clear signal repeater relay, designated by the reference character DP with, a prex which is the same as the prefix in the reference chara actor for i-ts signal. As also. shown for signals 3S and 8S, a clear orcaution signal repeater; slow release relay, designated by the reference character I-IDP with a prefix corresponding to` that of its signal, is controlled by contacts I5v and I6 of each enteringsignal and by the associated clearrepeater relay DP. A clear or caution signal repeater slow pick-up and slow release relay. designated by the reference character HDP, with a preexl correspondingrto that in the reference character for each leaving signal and for each intermediate signal, is controlled by contacts I5- and I of the correspond-ing leaving or interme` diate signal.

A polar biased code repeating relay SCTP shown in the lower left hand end of Fig. 1a, is selectivelyV controlled by signal repeater relays 3DP and BHDP to be energized by current of one of three diierent codes such, for example, as codes having frequencies of '75, 1-20, or 180. times per minute. Current of these different codes is provided by interruption of current from a suitable source, having terminals B and N, through contacts of code transmitters designated bythe reference characters 5CT, IZGCT, and IBDCT, respectively. Y As is well known, the point of arrival of a train at which a iloater track relay releases after the train enters the associated track section at the opposite end is variable. Each of the entering signals in applicants arrangement is controlled in part by the floating track relay which is adjacent the oppositel entering signal, and is therefore provided with a variable. overlap con-- trol.

At the intermediate signal location, a signal slow pick-up and slow release relay, designated by the reference character SHR', is energized by current from the secondary winding 1L of a de-. coding transformer 5F when current of any one ofthe thrs'e codes is supplied to the primary winding y of transformer SF in response to the control of relay STR by current of a corresponding code received from track section ST. A decoding relay SDRB is selectively controlled through a resonant decoding unit IZDDU so as to be operated only by current of 120 code supplied in response to operation of relay STR. A second decoding relay SDRA is controlled through a second resonant decoding unit I80DU so as to be operated only by current of 180 code supplied in response to operationof relay STR.

f A pole-changer slow release relay SPC is controlled by front contacts of relays SDRA and SDRB to be energized when either of these two decoding relays is energized.

An arc suppressor arrangement, designated by the reference character SU, is employed in conjunction with circuits controlled by contact 24 of relay STR, and a similar arc suppressor arrangement SU s employed in conjunction with circuits controlled by Contact 24 of relay STR.

Mechanism Sm of signal SS is controlled by relays SHR and SDRA to be operated-to the clear position only when relay STR is energized by current of 180 code received from section ST, and to be operated to the caution position when relay STR is energized by current of 7S or 120 code received from section ST.

Relays SHR, SDRB and EDRA are controlled by relay STR similarly to the manner in which relays lSHR, SDRB and SDRA, respectively, arev controlled by relay STR as just described. Relay IiPCl is also controlled similarly to relay SPC, and mechanism 6m of signal GS is controlled similarly to mechanism Sm of signal SS.

" A directional stick relay, designated by the reference character SSR, is controlled to become energized when a westbound train deenergizes relay SHR upon entering section ST, and is then controlled to remain energized as long as relay `SHDP remains deenergized. A second directional stick relay, designated by the reference character BSR, is controlled by eastbound trai-hc movements similarly to the manner in which relay SSR is controlled by westbound tralc movements. i

-Mechanism Im of leaving head block signal 1S is controlled by relay SPC to be operated to the clear positiononly when relay SPC is energized. As previously described, relay SPC' is energized only when current of 120 or 180 code is received by-relay STR from sectionST, that is, when signal 3S is controlled to display either the clear or the caution indication. Mechanism 4m` of leaving head block signal 4S is controlled simidetail, its operation.

As shown in the drawings, all parts of the apparatus are in the normal condition, that is, each signal mechanism m is controlled for displaying a clear` indication; all track sections are unoccupied, and hence all track relays are, energized; the current by which the code following track relays STR, STR, SATR, SATR, SATR and IIATR are energized is coded at the 180 frequency; the relays 3DP, 8DP, IHDP, 3HDP, 4HDP, SHDP, GH'DP, 'IHDPBHDR IDI-IDP, SHR, SPC, SHR, and SPC, and code transmitters I 80CT, IZSCT, and 'ISCT are energized; each of the relays IlAFP, IIABP, SAFP, SABP, SDRA, SDRA, SABP, SAFP, IIABP, IIAFP, SCTP and SCTP is energized by current of 180 code; each ofthe signal mechanisms m is energized by current of normal polarity; and each of the relays SDRB,

GDRB, SSR and SSR is deenergized.

The circuit by which relay 3DP is energized passes from terminal B, through the front point of contact I5 of signal 3S, and the winding of.` relay 3DP to terminal N. Relay 3HDP is ener` gized by a circuit passing from terminal B, through contact I1 of relay 3DP, and the winding of relay BHDP to terminal N. Relays 8DP and 8I-IDP are energized similarly to `relays 3DP and SI-IDP, respectively, as just described.

Relay IHDP is energized by a. circuit passing from terminal B, through the front point of con-v tact I5 of signal IS, and the winding of relay I HDP to terminal N. Relays 4HDP, SHDl?,

BI-lDP, 'IHDP, and IUHDP are energized by cir'" cuits which are similar to the circuit traced for relay IHDP.

Each of the code transmitters ISSCT, I20CT, and 'ISCT is connected directly across terminals B and N, and is therefore constantly energized. Each code transmitter I-CT, therefore, re-` peatedly opens and closes its contact I8 at a frequency of 180 times per minute. Each of the code transmitters I20CT repeatedly opens and closes its contact I9 at a frequency of 120 times per minute, and each of the code transmitters 'ISCT repeatedly opens and closes its contact 20 at a frequency of '75 times per minute.

Relay SCTP is energized by coded current of the 18o frequency passing from terminal B, through contact I8 of a code transmitter ISSCT, from point of lcontact 22 of relay 3DP, and the winding of relay SCTP Ain multiple with a regulating resistor t to terminal N. Contact SCTP- 23 of relay SCTP therefore repeatedly closes alternately at its front and back points 180y times per minute.

Current of the 180 code is therefore supplied to section ST from a battery I4, through the front point of contact SCTP-23. Relay SCTP is ener-` gized similarly to relay SCTP, and therefore current of the 180 code is also supplied to section 6T from a battery I4 through the front point of contact SCTP-23.

Relay STR is energized by current of the 1801 code received from section ST. Current is therefore supplied from terminal B, through contact 24 of relay STR to primary winding y of decoding transformer SF repeatedly in opposite directions at a frequency of 180 times per minute. The current thereby generated in secondary winding n of transformer SF is rectified by a contact 2S of relay STR for energizing relay SHR in multiple with aresistor r which makes relay SHR slow in releasing. Relay SDRB, on account of being.A controlled through a decoding unit I 20DU, does not respond to the current of frequency supplied through contact 24 of relay STR, but relay SDRA, on account of being controlled through a 180 decoding unit I SBDU, closes itsv front contacts in response to the current of `180 frequency supplied through contact 24 of relay. STR. Relay SPC is therefore energized by a circuit passing from terminal B, through contact 26 of relay SDRA, and the winding of relay SPC jto` terminal N. Relays STR, GHR, SDRA, and SPC are energized similarly to relays STR, SHR, SDRA, and SPC as just described.

With relays SDRA and SHR energized, the mechanism Sm of signal SS is retained in the; clear position by a circuit of normal polarity pass-:I

75 ing from terminal B, through the front point of cntactzaof relay-EDRA, ,contact 2.9 of relay SHRr mechanism 5m. 'and the front point of contact 3Qjofrelay DRAJJo terminal N. Signal mechanism 6m is energized similarly to mechanism 5m..

Mechanism 4m of signal 4S is energized by currentof normal polarity for'retaining mechanism 4m; in its clear position by a circuit passing froml terminal B, through the front point of contact BPC-3 I front point of contact MIDP-32, mechanismdrmcontact 33 of relay ESR. contact 3c of relay EHR. and front points of contacts SHDP--35 and SPC- 36 to 'terminal N. Mechanism 1m of signal 1S is energized similarly to mechanism 4m.

Floating track relay 5ATR is energized by currenti of 180 code supplied to section 5T by battery I4 through the front point of contact 5CTP23, and therefore contact 31 of relay SATR is repeatedly closed alternately at its front and back points at a frequency of 180 times per minute. Relay 5AFP is repeatedly energized by pulses of current passing from terminal B, through the front point of Contact 31 of relay '5A-TR, and the winding of relay EAFP in multiple withv a resistor r to terminal N. Relay SAFP is made slow releasing by resistor r connected in multiple with its winding, and therefore its contact 33 remains closed during the open periods of contact 31 of relay EATR at its front point. Relay EABP is energized by pulses of current passing from terminal B, through the back point of contact 31 of relay 5ATR, contact 38 of relay SAFP, and the winding of relay SABP, with a resistor r connected in multiple with contact 38 of relay SAFP and the winding of relay SABP, to terminal N. Relay EABP is also made slow releasing; by resistor 7' connected in multiple with its WindingL so that the front contacts of relay EABP remain closed during the intervals when contact 31 of relay EATR is open at the back point. Relays GATR, BAFP, and ABP are energized similarly to relays ATR, AFP, and ,5ABP. Each of the floating track relays @ATR and I IATR is energized by current of 180 code supplied to section T or IIT, respectively, by an associated battery I4 through the front point of a contactV I8 of an associated code transmitter IBCT. Contact 31 of each of the relays EATR and IIATR is therefore repeatedly closed alternately at its front and back points at a frequency of 180 times per minute. Relays EBAFP and IIAFP are energized similarly to relay EAFP, and relays OABP and IIABP are energized similarly to relay ABP.

Mechanism 2m of signal 2S is energized by current of normal polarity for retaining this mechanism in the clear position, through a circulti passing from terminal B, through the front point of contact 39 of relay fil-IDP, contact ABP-ll, contact 4I of relay STR, contact 42 ofv relay 2TR, mechanism 2m, and the front point ofcontact 45 of relay IHDP to terminal N. Each of the mechanisms 3m, 8m, and 9m for signals 3S,.8S, and 9S, respectively, is energized similarly to mechanism 2m.

Weshall assume that, with apparatus embodying our invention as shown in the accompanying drawings, thus in the normal condition, an eastboundtrain passes the next pair of head block signals west of signal 2S, causing signal IS to indicate stop. With signal IS indicating stop, contacts I5 and I8 of this signal are both open attheirrfront points, and therefore relay I HDP becomes. deenergized.

Withrelay IHDP deenergized, mechanism 3m becomes energized by currento reverse polarity in a circuit which is the same as the circuit previouslyV described for this mechanism except that itincludes the back points of contacts 39 andld of relay IHDP instead of the front points of these contacts. When mechanism 3m becomes energized by current of reverse polarity, contact l5 of signal 3S becomes opened at its front point and closed at its back point, and contact I6 of this signal becomes closed at its front point With contact I5 of signal 3S opened at its front point, relay SDP becomes deenergized, but relay SHDP is now energized by a circuit passing from terminal B, through contact I5 of signal 3S closed at its back point, contact I6 of signal 3S closed at its front point, and winding of relay 3HDP to terminal N.

With relay 3DP deenergized, the circuit previously traced for relay ECTP through contact22 of this relay becomes opened, and a second circuit is now completed for relay 5CTP, passing from terminal B, through contact I9 of a code transmitter IZlCT, front point of contact 2I of relay SHDP, back point of contact 22 of relay SDP, and the Winding of relay SCTP in multiple with a resistor t to terminal N. Relay SCTP is therefore now energized by current of code controlled by code transmitter IZBCT.

Current of 120 code is therefore now supplied to section 5T through the front point of contact SCTP-23. Relay 5TR is therefore energizedby current of 120 code frequency received from section 5T, and hence relay SDRB novv becomes energized and relay EDRA becomes deenergized, While relay SHR remains energized as before except by current controlled by the 120 code fre--v ouency instead of by the code frequency.

With relay EDRA deenergized, mechanism 5m is now energized by current of reverse polarity in a circuit which is the same as the circuit previously traced for this mechanism except that it .includes the back points of contacts 28 and 38 of relay 5DRA instead of the front points of these contacts.

With mechanism 5m thus operated to the caution position, the circuit previously described for relay SHDP is opened at the front point of contact I5 of signal 5S, but relay EHDP is now energized by a circuit passing from terminal B, through the back point of contact I5 of signal 5S, front pointY of contact I6 of signal 5S, and the winding of relay HDP to terminal N.

The circuit previously traced for relay 51C is now open at contact 2S of relay EDRA, but relay PC remains energized by a second circuit, passing from terminal B, through contact 21 of relay EDRB, and the winding of relay SPC to terminal N.

With relays SI-IDP and SPC thus energized, the circuit previously described for mechanism 1m is still closed, and therefore signal 1S continues to display the clear indication.

After the eastbound train has entered section' 8T and has proceeded part way through this sec ton,.the fioater track relay GATR adjacent signal 2S will become' deenergized similarly to floater track relay GATR, the operation of which will be traced later. Relay ABP will therefore be deenergized, making effective the overlap control for signal. 3S by deenergizing mechanism 3m .at contact 40 of relay EIABP.

- With mechanism 3m thus operated to the stop position, both contacts I5 and i3 of signal 3S will be opened at their front points, and hence relayy SHDP as `Wellnes SDP will be. deenergized.

;tacts 24 and 25 at a frequency of '75 times ,minute .Relay SHR will remain energized by current of Relay SCTP will therefore now be energized by `current of the 75 code frequency passing from terminal B, through contact 29 of code transmitter TSCT, back point of contact 2| of relay SHDP, back point of contact 22 of relay 3DP, and fthe winding of relay SCTP in multiple With resistor t to terminal N. Current of the 75 code `frequency will therefore now be supplied to section T through the front point of contact yIiCTP-23, and relay STR Will operate its con- Der this frequency, but relay SDRB as well. as relay SDRA will be deenergized. With relay SHR still energized, mechanism 5m of signal SS will remain energized by current of reverse polarity for retaining signal SS in the caution position.

1..;.1With both relays SDRB and SDRA deenergized, relay SPC will now also be deenergized, lcausing mechanism 1m to be energized by cur- .rent of reverse polarity in a circuit which is the same as the circuit previously described for this mechanism except that it includes the back points of contacts SPC-3! and SPC-36 instead ofthe front points of these contacts. Signal iS will therefore now indicate caution. The circuit by which relay 'II-IDP was previously energized through the front point of contact I5 will now be open, but relay 'IHDP will now remain energized by a circuit through the back point of contact IS and the front point of contact I 6 of `signal 1S. j Mechanism 9m of signal 9S will therefore remain energized by current of normal polarity.

-umWhen the eastbound train enters sectionlZT,

mechanism 2m will be deenergized because of the 'opening of contact 42 of relay 2TR. Signal 2S will therefore now display a stop indication.

When the train enters section 3T, the circuits for mechanisms 2mand 3m Will be opened at another point through contacts 4I and 44 of relay 3TR.

.When the train leaves section UT, relays IHDP and UABP Will become energized, but mechanism `3m will remain deenergized as long as the train `occupies section 2T or 3T, because of contacts 43 and'44 of relays 2TR and 3TR, respectively, be- "ing open.

When the trainV enters section 5T, relay SATR *will* become deenergized, and therefore relays 'SAFP and 5ABP will also be deenergized, rIhe .circuit for mechanism 2m Willtherefore now be penat another point because of the opening of contact 5ABP-4B.'

Relay STR will also become deenergized when .the train enters section 5T, and therefore relay SHR will be deenergized and open the'circuit for mechanism Sm, causing signal SS to'display a stop indication. stop position, rel-ay`SHDP will become deener- '-gized.. "111). vlWith relay SHR deenergized, 'the'circuit vfor :With mechanism'. ASm in the mechanism 4m is open at contact 34 of relay SHR, and hence mechanism 4m will move to the stop position, and relay 4HDP will become deenergized. With relay SHDP deenergized, the circuit for mechanism 'Im will be open at contacts SHDP-32 `and 5HDP-3S, and therefore mechanismlrrzl wil be operated to the stop position.

. Relay 'IHDP will therefore be deenergized, so

thatmech-anism 9m will be energized by current of reverse polarity and will be operated to the caution position. y

,When theftrain leaves section 3T, mechanism l10 3m will become energized by its circuit rst described, and therefore signal 3S will display the clear indication. The circuit for mechanism 2m will, however, still remain open, because relay 5ABP will remain deenergized until the train has proceeded part Way through section ST.

When the train enters section 6T, relay GTR will become deenergized, but relay SATR Will remain energized until the train has proceeded part Way through section 6T. With relay ETR deenergized, relay GDRA and, in turn, also relay -BPC Will be deenergized,

With relay GHR also deenergized, on account of relay STR being deenergized, relay SSR will become energized4 by a pickup circuit passing from terminal B, through the back point of contact SSR-4S, contact 41 of relay SHR, front point voi. contact 48 of relay BHDP, contact SHDP-49,

and the winding of relay SSR to terminal N. Relay BSR, upon becoming energized, completes a stick circuit which is the same as the pickup cir,-

Aready open at contact SHDP-3S.

cuit just traced except that it includes contact 5D of relay GSR, instead of contact 48 of relay SHDP and contact SHDP-49.

Relay EHR, upon becoming deenergized, also opens the circuit for mechanism Sm, causing signal SS to display the stop indication. With signal BS indicating stop, relay BHDP will become deenergized and complete a second stick circuit for relay SSR, this circuit passing from terminal B, through the back point of contact SSR-46, back point of contact 48 of relay GHDP,

-contact S0 of relay SSR, and the winding of relay points of contacts 39 and 4S of relay 4HDP.

When the train has passed part way through section 6T, relay SATR will become deenergized, and hence relay SABP will also become deenergized and cause the mechanism of signal 9m-to move to the stop position similarly to the manner previously described for mechanism 3m.

When the train leaves section 5T, relay STR. will again become energized, causing 'relays SHR and SDRA to Yalso in turn become energized.

.Mechanism Sm will therefore again becomeen'- ergized' by current of normal polarity, causing y'signal SS toA display the clear'indication. Relays SHDP-and vSPC Vwill then become energized." as previously described. Mechanism 4m will now become energized by current of reverse polarity passing from terminal B, through the front point of contact BSR-4S. back point of contact 6HDP`3S, contact 34 of relay SHR, contact 33 of relay SSR, mechanism 4m, and the back point of contact 6HDP--32 to terminal N. Signal 4S will therefore nowv display the caution indication, and relay 4HDP will again become energized and complete the circuit for'again energizing the circuit for mechanism 2m by current of normal polarity.

Signal 2S will therefore now again display the clear indication.

vAs they train now proceeds further, the opera- -tion of the signals at siding W will be 'similarto that already described for the signals at siding X. When mechanism 8m becomes deenergized by the train on section 8T, relays BDP and fil-IDP will 'become deenergized, and relay SCTP will then 5' become energized by coded current of the 75 frequency passing from terminal B, through conftact 20 of code transmitter 15CT, back point of contact 2| of relay SHDP, back point of contact i221 of relay 8DP, and the winding of relay SCTP `in multiple with resistor t to terminal N.

When the train now leaves section 6T, relay STR will therefore be energized by current of the '75 code, and hence relay EHR. will again be -energized and mechanism 6m will be energized by current of reverse polarity in its circuit which now includes the back points of contacts 28 and A30 of relay SDRA instead of the front points of these contacts. 'caution indication, relay BHDP will become envvergized and open its contact 48 at the back point, -vthereby deenergizing relay BSR. Relay SPC will 'still be deenergized, and therefore mechanism 4m With signal GS displaying the will still remain in the caution position.

With relay SHR again energized and relay GSR 'deenergized, mechanism 'im will now be energized by current of normal polarity in its circuit first described.

As the train proceeds further after entering Ysection IIT, the iioating track relay IIATR for section I IT will become energized and cause relay IIABP to again be energized. Mechanism 8m will then become energized by current of reverse polarity, and hence relay SHDP will vagain become energized.

With relay Si-IDl?v energized and relay BDP deenergized. relay SCTP will be energized by cur- -rent of 120 code passing from terminal B, through contact I9 of a code transmitter IZQCT, front point of contact ZI of relay BHDP. back point of contact 22 of relay BDP, and the Winding of relay SCTP in multiple with a resistort to terminal N.

'Relay ETR will therefore now be energized by coded current of 120 frequency, and hence relays SHR and DRB will again become energized.

With relay EDRA now deenergized and relay GHR energized, mechanism 6m will become energized by current of reverse polarity for operating condition, and that a westbound train enters section IIT While an eastbound train is between signal 2S and signal 4S at siding X. Signal @S v.will continue to display the clear indication until the westbound train arrives at a point at which the floating track relay I IATR for section IIT -releases and causes relay I IABP to be deenerlgized.

When relay I I ABP becomes deenergized, mech- .anism 8m becomes deenergized by the opening of contact 4i) of relay IIABP, and therefore signal Mechanism 6m will therefore be energized by current of reverse polarity, and hence signal GS willdisplay the caution indication.

Relay BPC will be deenergized because both relays SDRB and EDRA sare; .deenergized .and

-SS indicates stop. Relays fil-EDP and SDP will .therefore be deenergized, and' hence relay IiCTP will be` energized by current of the code.

" therefore mechanism 4m will be energized by current of reverse polarity, and signal 4S will display the caution indication for the eastbound train.

With the eastbound train between signals 2S and 4S, mechanism 3m will be deenergized, and therefore current of the 75 code will be supplied to section 5T, and signal 'IS will therefore display the caution indication for the westbound train.

We shall next assume that an eastbound train has just passed signal ES, and a Westbound train vhas just passed the first intermediate signal east -oi signal IES. V/"ith both relays SABP and I IABP energized, mechanisms 9m and 8m will be energized by current of reverse polarity, and therefore signals 3S and 9S will display the caution indication.

When the westbound train arrives at the point at which the floating track relay l IATR for section IIT becomes deenergized, relay IIABP will becomev deenergized, and hence signal 8S Will display the stop indication for the eastbound train. When the eastbound train arrives at the point at which relay BATR becomes deenergized, relay GABP will also become deenergized, and therefore signal 9S will be controlled to display the stop indication for the westbound train.

We have described the operation of the apparatus for a few typical traiiic movements. It is believed that, in view of this description, the operation of the apparatus for anyother possible traffic movement can be readily understood by reference to the drawings.

Although We have herein shown and described only one form of apparatus embodying our invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of our invention.

Having thus described our invention, what we claim is:

1. In a control system for signals for a stretch of single track railway including a rst pair of signals adjacent a given end of said stretch and a second pair of signals adjacent the opposite end of said stretch, a given signal of each of said pairs arranged for governing trafc movements onto said stretch and the other signal of each of said pairs arranged for governing trafc movements off of said stretch, and including a pair of intermediate signals between said first and second pairs of signals one for governing traiiic movements in a given direction over a rst section of said track between said rst pair of signals and said intermediate signals and the other for governing traffic movements in the opposite direction over a second section of said track between said second pair of signals and said intermediate signals, the combination comprising, means controlled in conjunction with each of said signals which governs trafc movements off of said stretch for supplying current of a first or a second or a third code to the adjacent said i'irst or said second section according as the associated said signal for governing traic movements oii of said stretch is controlled to display a clear or a caution or a stop indication respectively, means controlled by the track circuit for each of said sections when energized by current of said rst code for controlling the associated intermediate signal to display a clear indication, means controlled by the track circuit for each oi said sections when energized by current of said second or said third. code for controlling the associated 'intermediate signalto display a caution indication, and a line circuit for each of said 'given signals controlled by said coded track circuits for controllingits signal to display a clear indication if the adjacent track circuit is suppliedV with current of any one of said three codes while the :other track circuit is supplied with current of said rst or second codes and for. controlling its ,signal to display aai/caution indication if the ad- Ajacent track circuit is supplied with current of any oneof said three codes while the other'track circuit is deenergized by a train moving toward the other given signal or is supplied with current of said third code.

2. In a control system for railway signals for a stretch of single track railway which is provided -wth passing sidings spaced along the single track, including two pairs of head block signals for each passing siding each comprising an enter- -ing and a leaving signal one pair adjacent each vend of its passing siding for governing traffic -movements in opposite directions, including a -pair of intermediate signals between each two consecutive passing sidings for governing traiilc `movements in opposite directions, the combination comprising, two non-coded track circuits between Vthe two pairs of head block signals for 'each passing siding, two coded track circuits between each two consecutive passing sidings one ,between each of the passing sidings and the associated pair of intermediate signals, two v"traffic controlled line circuits :between the two pairs of head block signals at each passing siding, "a'traflic controlled line circuit between each pair -ofintermediate signals and the next pair of head vblock signals in each direction, and means controlled by said track circuits and by said line `circuits for controlling said head block and intermediate signals including overlapping clear con'- trol means for each twoopposing leaving head block signals.

3. In a control system for railway signals for a stretch of single track railway which is provided with passingsidings spaced along the single track, including two pairs of head block signals :for each passing siding each comprising an entering and a leaving signal one `pair adjacent each end of its passing siding for governing traiiic movements in opposite directions, including a ,pair of intermediatesignals between each two fconsecutive passing lsidings for governing trail-lc movements in opposite directions, the combination comprising, two non-coded track circuits between the two pairs of head block signals for each passing siding, two coded track circuits between each two consecutive passing sidings one between each of the passing sidings and the associated pair of intermediate signals, traffic controlled line circuit means including four line conductors between the two pairs of head block signals at each passing siding and two line conductors between each pair of intermediate signals and the next pair of head block signals in each direction, and means controlled by said track circuits and by said line circuit means for controlling said head block and intermediate signals including overlapping clear controls for each two opposing leaving head block signals.

4. In a control system for railway signals for a stretch of single track railway which is provided with passing sidings spaced along the single track, including two pairs oi head block signals for each passing siding each comprising an enteringand a leaving signal onepair adjacent each end lof Vits passing siding forgovernins trafc movements in opposite directions, including a pair of intermediate signals between each two consecutive passing sidings for governing traffic movements in opposite directions, the combination comprising, control means for each of said entering signals controlled by traflic conditions between its entering signal and the next leaving Asignal in advance and by pole changing means operated in conjunction with the next leaving signal in advance, means controlled in conjunction with each entering signal for supplying current of a rst code or a second code or a third code to a track circuit between the entering signal and the next intermediate signal in the rear according as the entering signal is controlled to ,display a clear or a caution or a stop indication -respectively, means for controlling each of said intermediate signals by the coded track circuit over which vit governs traic movements to dis'- play a clear indication if its track circuit is energized by current of said first code and to display a caution indication if its track circuit is energized by current of said second or said third code, means for controlling each of said leaving signals todisplay a clear indication if the track is unoccupied between the leaving signal and the next intermediate signal and if the next intermediate signal which governs traiic movements in the same direction is controlled to display either a clear or a caution indication while currentof either said first or said second code is being supplied to said ltrack between said next interme- -diate signal and the next opposing leavingv signal, and means for controlling each of said leaving signals to display a caution indication if the `track is unoccupied between the leaving signal and said next intermediate signal and if current of said third code is being supplied to the track between said next intermediate signal and said next opposing leaving signal.

5. In a control system for railway signals fo `a stretch of single track railway which is provided with passing sidings spaced alongthe single track, including two pairs of head block signals 'for each passing siding eachlcomprising an entering and a leaving signal one pair adjacent each end oi' its passing siding for governing traiiic '-'movements in opposite directions, including apair of intermediate signals between each two consecutive passing sidings for governing traffic 'movements in opposite directions and includinga -iirst section of said track between each pair of intermediate signals and the next pair of head block signals in a given direction from said intermediate signals and a second section of said track between each pair of intermediate signals and the next pair of head block signals in the opposite drection from said intermediate signals,

the combination comprising, means controlled inV coniunction with each entering signal for supplying current of a first or a second or a third code to the adjacent end of the adjacent said rst or se^ond track section according as the entering signal is controlled to display a clear 0r a caution or a stop Aindication respectively, a floating track relay connected adjacent each leaving signal across the adjacent said rst or second track section, control means for each of said entering signals controlled by traic conditions between the entering signal and the next leaving signal in advance and by the floating track relay which is adjacent the next leaving signal in advance and also by pole-changing means operated in conjunction with the next leaving signal in advance, means for controlling each of said intermediate signals by current of said first code received from the section over which it governs traic movements to display a clear indicat`.on and by current of said second or third code received from the same section to display a caution indication, and means for controlling each of said leaving signals if the rst track section in advance is unoccupied to display a clear indication if current of said rst or said second code is received from the second section in advance and to display a caution indication if current of said third code is received from the second section in advance.

' 6. In a control system for railway signals for a stretch of single track railway which is provided with passing sidings spaced along the single track, including two pairs of head block signals for each passing siding each comprising an entering and a leaving signal one pair adjacent each end of its passing siding for governlig trafic movements in opposite direction, including a pair of intermediate signals between each two consecutive passing sidings for governing traino movements in opposte drections, and including a rst section of said track between each pair of intermediate sig- .nals and the next pair of head block signals in a given direction from said intermediate signals and a second section of said track between each Apair of intermediate signals and the next pair of head block signals in the opposite direction from said intermediate signals, the combination comprising, means controlled vin conjunction with each entering signal for supplying current of a first or a second or a third code to the adjacent end of the adjacent said rst or second track section according as the entering signal is controlled to display a clear or a caution or a stop indication respectively, means for controlling each of said entering signals according to traic conditions in advance, means for controlling each of said intermediate signals by current of said virst code received from the section over which it governs traine movements to display a clear indication and by current of said second or said thi-rd code received from the same section to display a caution indication, and means for controlling each of said leaving signals if the first track section in advance is unoccupied to display a clear vindication if current of said rst or said second .code is received from the second section in advance and to display a caution indication if curirent of said third code is received from the second jsection in advance.

7. In a control system for railway signals for a stretch-,of single track railway which is provided with passing sidings spaced along the single track, including two pairs of head block signals for each passing siding each comprising an entering and a leaving signal one pair adjacent each end of its passing siding for governing trailc movements in opposite directions, including a pair of intermediate signals between each two consecutive passing sidings for governing traic movements in opposite directions, and including a iirst section of said track between each pair of intermediate signals and the next pair of head block signals in a given direction from said intermediate signals and a second section of said track between each pair of intermediate signals and the next pair of head block signals in the opposite direction from said intermediate signals, the combination comprising, means controlled in conjunction with each entering signal for supplying current of a first or a second or a third code to the adjacent end of the adjacent said rst or second track section accordlng as the entering signal is controlled to display a clear or a caution or a stop indication respectively, means for controlling each of said entering signals according to traffic conditions in advance; means for controlling each of said intermediate signals by current of said iirst code received from the section over which it governs trame movements to display a clear indication and by current of said second or third code received from the same section to display a caution indication, means including current of said rst or said second code received from the second section in advance for controlling each of said leaving signals to display a clear indication, and means including current of said third code received from the second seLtion in advance for controlling each of said leaving signals to display a caution indication.

WILLIAM H. CLAUS. JAMES H. BUTRIDGE.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,014,015 Blosser Sept. 10, 1935 2,352,800 Peging July 4, 1944 

